1. Field of the Invention
The present invention relates to flexible, lightweight, air impermeable coated fabric which exhibits excellent resistance to flame and abrasion but which can be fabricated using heat (or dielectric) sealing procedures.
In the field of space exploration, high strength, flame retardant, abrasion resistant and leakproof materials are required for construction of clothing and containers e.g. bags. Such materials must have good strength and flexibility over the temperature and pressure ranges normally encountered in such endeavors. Additionally, because of the likelihood of encountering high oxygen content atmospheres, the materials must be flame retardant. Further, the garments, bags, etc. constructed from such materials must be leakproof to avoid loss of the life support atmosphere during periods of low pressure which may be experienced in a spacecraft.
2. Description of the Prior Art
In the prior art, as exemplified by U.S. Pat. Nos. 3,833,540; 3,956,233; 3,847,723; 3,202,567; 3,455,850; 3,954,701; 3,786,087; and 3,821,067, the use of flame retardant fillers and chemicals compounded with synthetic thermoplastic polymers to form compositions which have improved flame retardant properties is well known. It is also known, as shown in the references, to coat various fabrics with such compositions to produce flame retardant coated fabrics.
U.S. Pat. No. 3,956,233, to Fletcher et al, discloses elastomeric polymers compounded with flame retardant fillers to produce films and fibers having good flame retardant properties. Fletcher et al discloses that conventional polyurethanes of both the polyether and polyester types can be blended with fire retardant additives, particularly halogenated compounds and organic phosphorus containing compounds, to produce elastomer films and fibers exhibiting good flame retardant properties. Example IV of Fletcher et al discloses compositions of Lycra spandex polyurethane with various flame retardant additives. As can be seen from Table I of Fletcher et al, the additives severely reduce the tensile strength of the elastomeric compound compared to the original Lycra polyurethane.
The prior art does not disclose the flame retardant additive compositions of the present invention which, when blended with soluble, thermoplastic polyurethanes of the polyether or polyester type produce elastomeric compositions, which in addition to being flame retardant, also possess good abrasion resistance, flexibility, and heat sealing properties. In general, the flame retardant additives disclosed in the prior art reduce abrasion and tear resistance (tensile strength) and flexibility when blended with polyurethane polymers. Also, the flame retardant additives of the prior art, at loadings required to impart good flame retardant properties to soluble, thermoplastic polyurethanes, tend to severely reduce the heat sealing properties of the polyurethanes.